drivers/i2c/busses/i2c-stub.c

   1 /*
   2     i2c-stub.c - I2C/SMBus chip emulator
   3
   4     Copyright (c) 2004 Mark M. Hoffman <mhoffman@lightlink.com>
   5     Copyright (C) 2007 Jean Delvare <khali@linux-fr.org>
   6
   7     This program is free software; you can redistribute it and/or modify
   8     it under the terms of the GNU General Public License as published by
   9     the Free Software Foundation; either version 2 of the License, or
  10     (at your option) any later version.
  11
  12     This program is distributed in the hope that it will be useful,
  13     but WITHOUT ANY WARRANTY; without even the implied warranty of
  14     MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  15     GNU General Public License for more details.
  16
  17     You should have received a copy of the GNU General Public License
  18     along with this program; if not, write to the Free Software
  19     Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
  20 */
  21
  22 #define DEBUG 1
  23
  24 #include <linux/init.h>
  25 #include <linux/module.h>
  26 #include <linux/kernel.h>
  27 #include <linux/slab.h>
  28 #include <linux/errno.h>
  29 #include <linux/i2c.h>
  30
  31 #define MAX_CHIPS 10
  32
  33 static unsigned short chip_addr[MAX_CHIPS];
  34 module_param_array(chip_addr, ushort, NULL, S_IRUGO);
  35 MODULE_PARM_DESC(chip_addr,
  36                  "Chip addresses (up to 10, between 0x03 and 0x77)");
  37
  38 static unsigned long functionality = ~0UL;
  39 module_param(functionality, ulong, S_IRUGO | S_IWUSR);
  40 MODULE_PARM_DESC(functionality, "Override functionality bitfield");
  41
  42 struct stub_chip {
  43         u8 pointer;
  44         u16 words[256];         /* Byte operations use the LSB as per SMBus
  45                                    specification */
  46 };
  47
  48 static struct stub_chip *stub_chips;
  49
  50 /* Return negative errno on error. */
  51 static s32 stub_xfer(struct i2c_adapter * adap, u16 addr, unsigned short flags,
  52         char read_write, u8 command, int size, union i2c_smbus_data * data)
  53 {
  54         s32 ret;
  55         int i, len;
  56         struct stub_chip *chip = NULL;
  57
  58         /* Search for the right chip */
  59         for (i = 0; i < MAX_CHIPS && chip_addr[i]; i++) {
  60                 if (addr == chip_addr[i]) {
  61                         chip = stub_chips + i;
  62                         break;
  63                 }
  64         }
  65         if (!chip)
  66                 return -ENODEV;
  67
  68         switch (size) {
  69
  70         case I2C_SMBUS_QUICK:
  71                 dev_dbg(&adap->dev, "smbus quick - addr 0x%02x\n", addr);
  72                 ret = 0;
  73                 break;
  74
  75         case I2C_SMBUS_BYTE:
  76                 if (read_write == I2C_SMBUS_WRITE) {
  77                         chip->pointer = command;
  78                         dev_dbg(&adap->dev, "smbus byte - addr 0x%02x, "
  79                                         "wrote 0x%02x.\n",
  80                                         addr, command);
  81                 } else {
  82                         data->byte = chip->words[chip->pointer++] & 0xff;
  83                         dev_dbg(&adap->dev, "smbus byte - addr 0x%02x, "
  84                                         "read  0x%02x.\n",
  85                                         addr, data->byte);
  86                 }
  87
  88                 ret = 0;
  89                 break;
  90
  91         case I2C_SMBUS_BYTE_DATA:
  92                 if (read_write == I2C_SMBUS_WRITE) {
  93                         chip->words[command] &= 0xff00;
  94                         chip->words[command] |= data->byte;
  95                         dev_dbg(&adap->dev, "smbus byte data - addr 0x%02x, "
  96                                         "wrote 0x%02x at 0x%02x.\n",
  97                                         addr, data->byte, command);
  98                 } else {
  99                         data->byte = chip->words[command] & 0xff;
 100                         dev_dbg(&adap->dev, "smbus byte data - addr 0x%02x, "
 101                                         "read  0x%02x at 0x%02x.\n",
 102                                         addr, data->byte, command);
 103                 }
 104                 chip->pointer = command + 1;
 105
 106                 ret = 0;
 107                 break;
 108
 109         case I2C_SMBUS_WORD_DATA:
 110                 if (read_write == I2C_SMBUS_WRITE) {
 111                         chip->words[command] = data->word;
 112                         dev_dbg(&adap->dev, "smbus word data - addr 0x%02x, "
 113                                         "wrote 0x%04x at 0x%02x.\n",
 114                                         addr, data->word, command);
 115                 } else {
 116                         data->word = chip->words[command];
 117                         dev_dbg(&adap->dev, "smbus word data - addr 0x%02x, "
 118                                         "read  0x%04x at 0x%02x.\n",
 119                                         addr, data->word, command);
 120                 }
 121
 122                 ret = 0;
 123                 break;
 124
 125         case I2C_SMBUS_I2C_BLOCK_DATA:
 126                 len = data->block[0];
 127                 if (read_write == I2C_SMBUS_WRITE) {
 128                         for (i = 0; i < len; i++) {
 129                                 chip->words[command + i] &= 0xff00;
 130                                 chip->words[command + i] |= data->block[1 + i];
 131                         }
 132                         dev_dbg(&adap->dev, "i2c block data - addr 0x%02x, "
 133                                         "wrote %d bytes at 0x%02x.\n",
 134                                         addr, len, command);
 135                 } else {
 136                         for (i = 0; i < len; i++) {
 137                                 data->block[1 + i] =
 138                                         chip->words[command + i] & 0xff;
 139                         }
 140                         dev_dbg(&adap->dev, "i2c block data - addr 0x%02x, "
 141                                         "read  %d bytes at 0x%02x.\n",
 142                                         addr, len, command);
 143                 }
 144
 145                 ret = 0;
 146                 break;
 147
 148         default:
 149                 dev_dbg(&adap->dev, "Unsupported I2C/SMBus command\n");
 150                 ret = -EOPNOTSUPP;
 151                 break;
 152         } /* switch (size) */
 153
 154         return ret;
 155 }
 156
 157 static u32 stub_func(struct i2c_adapter *adapter)
 158 {
 159         return (I2C_FUNC_SMBUS_QUICK | I2C_FUNC_SMBUS_BYTE |
 160                 I2C_FUNC_SMBUS_BYTE_DATA | I2C_FUNC_SMBUS_WORD_DATA |
 161                 I2C_FUNC_SMBUS_I2C_BLOCK) & functionality;
 162 }
 163
 164 static const struct i2c_algorithm smbus_algorithm = {
 165         .functionality  = stub_func,
 166         .smbus_xfer     = stub_xfer,
 167 };
 168
 169 static struct i2c_adapter stub_adapter = {
 170         .owner          = THIS_MODULE,
 171         .class          = I2C_CLASS_HWMON | I2C_CLASS_SPD,
 172         .algo           = &smbus_algorithm,
 173         .name           = "SMBus stub driver",
 174 };
 175
 176 static int __init i2c_stub_init(void)
 177 {
 178         int i, ret;
 179
 180         if (!chip_addr[0]) {
 181                 printk(KERN_ERR "i2c-stub: Please specify a chip address\n");
 182                 return -ENODEV;
 183         }
 184
 185         for (i = 0; i < MAX_CHIPS && chip_addr[i]; i++) {
 186                 if (chip_addr[i] < 0x03 || chip_addr[i] > 0x77) {
 187                         printk(KERN_ERR "i2c-stub: Invalid chip address "
 188                                "0x%02x\n", chip_addr[i]);
 189                         return -EINVAL;
 190                 }
 191
 192                 printk(KERN_INFO "i2c-stub: Virtual chip at 0x%02x\n",
 193                        chip_addr[i]);
 194         }
 195
 196         /* Allocate memory for all chips at once */
 197         stub_chips = kzalloc(i * sizeof(struct stub_chip), GFP_KERNEL);
 198         if (!stub_chips) {
 199                 printk(KERN_ERR "i2c-stub: Out of memory\n");
 200                 return -ENOMEM;
 201         }
 202
 203         ret = i2c_add_adapter(&stub_adapter);
 204         if (ret)
 205                 kfree(stub_chips);
 206         return ret;
 207 }
 208
 209 static void __exit i2c_stub_exit(void)
 210 {
 211         i2c_del_adapter(&stub_adapter);
 212         kfree(stub_chips);
 213 }
 214
 215 MODULE_AUTHOR("Mark M. Hoffman <mhoffman@lightlink.com>");
 216 MODULE_DESCRIPTION("I2C stub driver");
 217 MODULE_LICENSE("GPL");
 218
 219 module_init(i2c_stub_init);
 220 module_exit(i2c_stub_exit);
 221